From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2F6BEC61DB9 for ; Fri, 28 Aug 2026 19:17:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 244636B0096; Fri, 28 Aug 2026 15:17:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 21B146B0098; Fri, 28 Aug 2026 15:17:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 158ED6B0099; Fri, 28 Aug 2026 15:17:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id E9C576B0096 for ; Fri, 28 Aug 2026 15:17:13 -0400 (EDT) Received: from smtpin20.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 7724FC0531 for ; Fri, 28 Aug 2026 19:17:13 +0000 (UTC) X-FDA: 85151636346.20.A14F04F Received: from relay.hostedemail.com (unirelay04 [10.200.18.67]) by imf17.hostedemail.com (Postfix) with ESMTP id A2C8D4000F for ; Fri, 28 Aug 2026 19:17:11 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; none ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787944631; b=NEvGFTQLk4ML5WdIrxagzYkPW1xcmn1Je++ntdrm1E9ExgIQvvMZ79C0QrS4g8a72FXfe3 0DNH6aiW4wN6P9Lu9m/AHe0J3xNAzRGqMffUUPI1fC3YaFDjqMSbu2O/4vGWrVpwGHCPFN eteo4hEQ62GaiZuGeEdthl3z2APOKfg= ARC-Authentication-Results: i=1; imf17.hostedemail.com; none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787944631; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=0RDwr71FlsrAMrAAlqln64IM9QGsxwXWA77DtZDfZwQ=; b=WFf4KCXfwmI1DTvYTOIzwS+fwJ+1ma343ofonBNCCNaOORmCymRu14LO+jKy9k9R40Trqn RjD3BJqeDxllcj04rp/surVvRJ5JRIUivfHUVdqyAG4NHtWpSWRGBT5jClq0Xe7stNw2m5 0OLjM61tFL4KZqCyvl2ynjDh8xEUF4s= Received: from omf05.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id C52951A053F; Fri, 28 Aug 2026 19:17:06 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf05.hostedemail.com (Postfix) with ESMTPA id C3E9F20011; Fri, 28 Aug 2026 19:16:57 +0000 (UTC) Date: Fri, 28 Aug 2026 15:17:47 -0400 From: Steven Rostedt To: Sebastian Andrzej Siewior Cc: Peter Zijlstra , David Stevens , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , Andrew Morton , Dave Chinner , Qi Zheng , Roman Gushchin , Muchun Song , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Uladzislau Rezki , David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Clark Williams , suleiman@google.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-rt-devel@lists.linux.dev Subject: Re: [RFC 06/10] Reclaim memory from blocked kernel stacks Message-ID: <20260828151747.20035d50@gandalf.local.home> In-Reply-To: <20260828151313.5c4a5e4b@gandalf.local.home> References: <20260827232948.2520558-1-stevensd@google.com> <20260827232948.2520558-7-stevensd@google.com> <20260828133620._x2XfJR_@linutronix.de> <20260828135947.GU776954@noisy.programming.kicks-ass.net> <20260828151018.HnR9xV1N@linutronix.de> <20260828150836.2d5b378c@gandalf.local.home> <20260828151313.5c4a5e4b@gandalf.local.home> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1/FRCRqi3s+JC4roW7NUQua3g10tn9P4XM= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=goodmis.org; h=date:from:to:cc:subject:message-id:in-reply-to:references:mime-version:content-type:content-transfer-encoding; s=dkim1; bh=0RDwr71FlsrAMrAAlqln64IM9QGsxwXWA77DtZDfZwQ=; b=gAZTVjGDveN8fhsH4aJV2blL0f0S/QpEEvr3BQpYaHupiEQdLMD69nFOfdLEk1spL0/g6lXtTnfNyIqHZGTSM2GCgE4DvzYvzij8bAWlZRrSpkm67+yI+NJTg387b0JmME/jtx2tEqWIUYUrCD2W7DFVoX4NatssuHtJiesq2nE= X-HE-Meta: U2FsdGVkX1+ViF3OvOgaM5ssQLR7tn0uySWJaFHYtcXWZ21cz7nnxMRW6iHpDWrp6Htrs0cIkgW4SbBQGFpZUf1ROkYnZEWGOtcWKXjDukDAh5xQHzSUkPxJbyaumnTpSqP3YXkkCipkNohafMlloaOqbdI5ACVjC77j7iGbrpU8lCltcFJhtONUqXBCJpw9eTajIr0/aLHn6NisdoeErwIxVK/oB2Np5iYGqcWQEGRVIxOt9i1N8E1VkhWj8uFuSoYqfpNN0eEmhPs7aE8vmz2WPbGl+v4Ry92BAG7LkkOQAqWIZjLFKEu432FqDcWspoc2zzLFnstcV5vVdG65ka7IObsOxeMhd+5KlkygWN4xwraefOr4pQuVKgzS9Rrd X-Rspam-User: X-Stat-Signature: j65tfsnn7wb96ijjjfomjeapo6aro4m7 X-HE-Tag-Orig: 1787944617-357454 X-Rspamd-Queue-Id: A2C8D4000F X-Rspamd-Server: rspam06 X-HE-Tag: 1787944631-539276 X-HE-Meta: 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 xj8SuvQ0 c4WEeDiYTAX1p6mRDoPB49gadblpE19P90GlwCdTXRpiUHzkx/Vo9OcfYtafHfYdvzr5R18Ract7Mcu4E2AVNLdsADiJU1APXfyc5seIsN6jF3k0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 28 Aug 2026 15:13:13 -0400 Steven Rostedt wrote: > If one worries about stack size, they may want to turn off > CONFIG_RANDOMIZE_KSTACK_OFFSET as I see some big numbers for do_syscall_64() And the scheduler has some heavy stack usage here! # trace-cmd stack (stack tracer running) Depth Size Location (31 entries) ----- ---- -------- 0) 8120 48 __msecs_to_jiffies+0x9/0x30 1) 8072 104 update_group_capacity+0x94/0x960 2) 7968 528 update_sd_lb_stats.constprop.0+0x426/0x39b0 3) 7440 424 sched_balance_find_src_group+0x8f/0x1150 4) 7016 552 sched_balance_rq+0x934/0x4130 5) 6464 408 pick_task_fair+0xa71/0x1fe0 6) 6056 496 __schedule+0x628/0x76f0 7) 5560 32 schedule+0xde/0x2c0 8) 5528 32 io_schedule+0x8c/0x100 9) 5496 256 rq_qos_wait+0x12b/0x230 10) 5240 136 wbt_wait+0x150/0x260 11) 5104 40 __rq_qos_throttle+0x51/0xa0 12) 5064 304 blk_mq_submit_bio+0xc40/0x28e0 13) 4760 240 submit_bio_noacct_nocheck+0x410/0xb30 14) 4520 40 ext4_io_submit+0xca/0x1a0 15) 4480 144 ext4_bio_write_folio+0x5e2/0x1470 16) 4336 96 mpage_process_page_bufs+0x392/0x700 17) 4240 616 mpage_prepare_extent_to_map+0xaae/0x1120 18) 3624 480 ext4_do_writepages+0x971/0x37f0 19) 3144 312 ext4_writepages+0x2d2/0x610 20) 2832 152 do_writepages+0x21e/0x560 21) 2680 184 __writeback_single_inode+0x119/0x1240 22) 2496 752 writeback_sb_inodes+0x67d/0x17b0 23) 1744 168 __writeback_inodes_wb+0xf2/0x270 24) 1576 304 wb_writeback+0x63e/0x890 25) 1272 320 wb_workfn+0x844/0xca0 26) 952 360 process_one_work+0x8b4/0x15d0 27) 592 176 worker_thread+0x5d3/0xfb0 28) 416 64 kthread+0x33c/0x420 29) 352 160 ret_from_fork+0x65c/0x9e0 30) 192 192 ret_from_fork_asm+0x1a/0x30 Note, I'm running this on my server. That is, this is a production machine. -- Steve